System of radiocommunication



Jan. 1, 1929;

- L. A. HAZELWNE 'SYSTEM OF RADIOCOMMUNICATION Filed Nqv. 1, 1917 Cafslglnl :Ilm u 00/ rig .f.

ATToBNEy Patented Jan. l' 1, 1929.

UNITED sTATEs'PATENT OFFICE.

Louis ALAN HAZELTINE, or HOBOKN, NEW JERSEY, AssrGNOn, BY masiva AssIGNManns. To waannanro, rive., A CORPORATION or DELAWARE.

- avaricia or RADIOOOMMUNIOATION.

lippnmipn anniimc-mbar4 1, 1917. `serial no. 199,743;

This invention relates to; radiocommunication, and more particularly ltooscillating audion circuits such as are used in receiving ortransmitting intelligence either by speak- 5 in telephone or bytelegraph.

n radio telephonyl andtelegraphy it is usual to employ one-set ofapparatus for transmitting and another setv for receiving at eachstation. This is done because with the Ordinary arrangements ofreceiving apparatus a comparatively large amount of incoming energy isrequired to giveeasil audible response, and this requires that t etrans' mittingapparatus deliver more out-put than 15, could beobtainedfrom a'n audion-Which is suited for receiving. Thus a large audion orother radio-fre uency generator is used for transmitting an a smallaudion, or other detector is used for receiving. y

In receiving sustained-wave` telegraphic signa-ls bythe heterodyne orheats method, it is necessaryl to have a loca-l oscillation otl alslightly dierent frequency from that of the incoming oscillation and itis usual to employ an audion both to produce this local oscilla tion andto act as the detectorLj It has been recognized that in this use of theaudion its sensitiveness as a detector is im roved by its being in theoscillating condition; but vapplication of this principle toradiotelephony presents special diiii'culties, which have not heretoforebeen overcome.` .A

I have discovered that vit is feasible to use `an oscillating audion asa detector' in radiotelephony, by employing methods and appa-l ratushereinafter described.' By reason `ot l the Superior sensitiveness ofthe oscillating audion as'a detector, I am thereby enabled to use a lesspowerful generator at the trans- 40 .mittingi'statiom with the verydesirable result that "under suitable circumstances the same audion maybe used both for transinitting and for; receiving. I have also discov.ered that this apparatus and some of the methods areadvantageously-applied to radio- `telegraphy, with the same result ofdecreasf ing the required .transmitting power.

Fundamentally the method of two-Way ra-44 diotelephoniccommunicationwith a single 5U oscillating audion at each stationconsists in operating these audions in synchronis'm. 1f

the audions are not in synchronism, fa beat note will be produced, or adistortion of the the extremely small ener 'voice tones, if the beatnote bebutside the audible range, causing the voice to be uninftelligible. Ihave discovered that two audions may be o ated insynchronism when connected in distant radio stations and thattransmitted from one station to theother is suiiicient to hold them insynchronism evenwhen the strength of the oscillation varies due to thevoice vibrations. v

In radio receiving apparatus employing an oscillating audion operatingin synclironism 05 with the incoming signal oscillation, it is desirablethat-the audion be able to readily change its freqency by smalll amountsso as to accommodate itself to accidental changes in the incomingfrequency. I have discov- .70 ered that audion receiving circuits of acertain general type and having certain numer ical relations between`the circuit constants have ythe property that the oscilla-tion producedby the audion will readil change its frequency with changes in therequencyof the oscillation impressed on the antenna so vas to keep thetwo oscillations in synchronism. This type of circuit and the necessaryrelation is given below. l

The receiving system consists of two tuned circuits, an antenna circuitin which the incoming signal oscillation is impressed, and a localcircuit connected or coupled to the au ldion. Theaudion may be connectedto the loca-l circuit in any of the various ways coinmonly known thatwill produce oscillations,

butY must either not be coupled to the antenna circuit at all, or elsecoupled very loosely thereto.` The antenna and local circuits may ao vbe coupled together by any of the methods commonly used, as mutualinductance, common self-inductance,` or common capacity.

If the coupling betweenv thev vantenna and4 loca-l circuits is closerthan a certain .transi-,os tion value, the-frequency of Oscillation willsuddendly change by a finite amount when the natural frequency ofone ofthese-circuits fis lgradually changed 'and passed throught e value vforthe :other circuitioo If, on` the 'other hand` the coupling 1s than;this transition value, the frequency of Oscillation 'will change onlygradually'when the natural fr uency of one of' thecircuits-is changed. Iave.v discovered' 105 that this particular condition of transit-ioncoupling is peculiarly valuable in radio receiving systems in that itpermits the synchronous operation referred to above.

In the accompanying drawing, n

Figure 1 "is a diagram of a. sendlng and receiving system,

`Figure 2 l.is a diagram of amodiied system adapted for longdistancegoperation,

Figure 3 is a diagram showing the saving in power by transitioncoupling, and

Figure 4 is a diagram showing the variation in radiation of-.energy@with diierent values of coupling. c

InfFigure-l, 1 is the antenna or external circuit containing! thevariable self-inductance coil 2 for tuning, and the variable seriescapacity 3,' connected to ground 4. Y Variably coupled to theself-inductance 2 is a coil 5, having one termina-l connected by wire 6to theplate 7' of an audion or Vother suitable relay deviceB. Thevariable coupling of these'coils may be attained by pivoting one coilrelativel to the other so that their axes can be variedy in theirrelative relation. 1" By Aaudio'nvis meant any evacuated vessel havingone hot and one or morevcold electrodes and acting as a relay, whereby arela- `tively'small alternating voltage supplied between one coldelectrode and the hot electrode, producesa relatively large alternatingcurrent andfvoltage in a circuit or circuits connected betweenthe `othercold electrode or electrodes and the 'hot electrode; As commonly used,the audion hasta rectifying action in addition to this rela oramplifying action, but for the purposes this invention, a separaterectifierV or detector may be employed if desired. :f 'The otherterminal of coil 5 is connected b wire 9 to self inductance 10, which isvariatile'as shownfor tuning this local circuit.

The other terminal of coil 10 is connected byV wire' 11 tothe positiveterminal of late battery 13. The negative side of thejattery isconnected to ground through the ammeter or other suitable currentindicator 14 and the telephone receivers 15. 18'is a capacity con nectedbetween vwires 6 and 11 around coil 10 to be usedin case the inherentcapacity of the audio'n and connected apparatus is insuicient toV makethe localcircuit resonant.

The circuit of grid 2f) is connectedby Wirey 21- to inductance 22v whichis variabl coupled `ment 29. By

to ind'uctance 10, constituting a variable grid coupling, then by wire23 to adjustable grid battery 24, then by Wire 25 to grid potentiometer26, and by ground and wire 34 to fila# varying battery 24, the strengthof oscillation is varied, and the potentiometer 26 gives fine controlofthe grid potential, coarse 'control being obtained by varying thenumber of vcells in battery 24.

32 is the heating battery connected to filament i 29. through resistance31, Wire 30, and by wire 34 to ground. t

It has been found that this conductive connection of'the grid 20 to thefilament 29 through the battery 24 and potentiometer 26 for adjustingitsaverage potential iscouducive to stability of the audion and hence togreater freedom from impulsive interference large compared with thealternating part of the grid potential, attained in Fig. 1 by tuning theplate circuit by the condenser 18 instead of timing the grid circuit, ashas been common practice heretofore, permits oscillations of relativelylarge power to be generated, while effectively retaining the detectingproperty of the audion.

In operating to receive signals," the audion is most sensitive as adetector when it is oscillating independently of the received sig'- nal,which is necessary in the heterodyne reception of sustained waves. on isoscillating however, certain li1nitations are imposed, which Varyfordiiferent forms of signals to be received, as in radio telephony, orradio telegraphy with damped waves, or radiotelegraphy with sustainedwaves. This invention is applicable for all of these purposes andpresents distinct and novel advantages over methods and systemsheretofore proposed.

To determine experimentally when the coupling has the desired transitionvalue, the` natural frequency of one of thecoupled circuits iscontinually varied through the tuning When an audiy point (i. e., thepoint at which the two circuits "o coupling is loosened so that theclick'or beat note and the jump in the ammeter reading just disappear,transition coupling has been attained. This procedure is the same nomatter whatform of coupling or what yaudion connection is employed, lsolong as the connections are of the type described above.

Mathe-matically there is a definite and' siniple relation between thetransition 'coupling and the other constants of the circuit and this is.that the. coetlicient coupling.l should 4equal the .power factorof theantenna Vvcir.- ciut. 'By ,cOeliiCient, coupling 1 with wli'erreM'lz' isthe mutual'inductance between the antenna n d vlocal circuits, whoseself# vinductances -are "L and, Iii .reS'P'eQtiYeIY-- By where 2.2 isthe'resistance-andgthe'capacity ofv the antenna ,circuit..;;lVithotheriormsof coupling the .j coeiicientuoff couplingM is Texpressed. byotherformulas, ybut its'sign-iic-ance would generally beI apparent toonei'a'iniliar with the theoryofcoupled circuits", audit vshould stillbe adjusted to equal the power factor, either X3-Oily 0r .with aninsignificant difference. .c Y

The curves of F the relation the voltage in the antennay required tomaintain synchronous operation,- plotted 'against the relative naturalvfrequencyfor-which the reza ceiving system is adjusted, for 'a powerfactor)v p2 ofthe antenna'circuit equal .to 0.01, andfor the threeCases: (ab)lof-:transition .couplingn marked c',f2=0.0l,; (b):otas'coup'ling of. twice the transition value, marked .c,jv2`-.f' 0.02;and (0) of a. coupling of one ha-lfthe transition value, marked 'c,2=0.005.. These*- curvesshow for example that if'the naturali frequency isoutof adjustment bjl/:ZO of 1% (pointsmt 09995 and.. 1.0005).thevoltagej in the antenna. that will .justf'maintain synchronous`operationis aboutlltimes'as Similar conditions l ariseA in receiving'dampedwave telegraphic signals. Dampedwaves are emitted in,cjroups-by'thesendingf ceivers which respondfmith a. musical tkme'having the group frequency. ,It is foundin practice'that an independent4oscillation .in the receiving apparatus will cause'the rel ceivedsignalsftobe-louder. but the musical note will be lost, andthe signalsthereby become less readable in the presence 'of "disturbances-,ss-uchas are' caused by strays. The

reason for this is that the local-oscillation* does@ not."cox'nbinefwith successive signal lgrroups--i`nt-he same phase, butsometimes adds to and'sometimes subtra'cts from the silz'nalloscillationvand in'varying amounts; This effect is similar 'ini itsgeneral characteristicsto radiotelep'hony receiving Aw1tl1 the-two os;J

P Y which-gives vthe desired'fmusical tone.

- telephone receiveizs,f;. and-sl cilla'tions out of synchronis'm, andis obviated 'toa considerable degreeby the same receiv- 'ingcircuitnsjandv relation betweenthe circuit ,n :constants- 'Thus Withcircuitsof the type previously described "(fof lwhich Fig'.l 1*is`v anexample)/and adjusted`-i`or transitiont coupling,gthe localoscillation'can readily change slightly in frequency and fso canaccommodate itselfn to. changesin'phasefot' the* successive groups. Inthis way the local oscilla-tion will addv to. *all* (or nea''lvfa'll )Vvof the groups arnd-.Will' greatly-am tl inf'without destroying' theiryregular er'it'idic'lcharacter Even in-.cases `WhereV itis not fou-nd'possible to. attain this synehronizinfc"action; it will be foundvdesirable adj'us h"' plingto the transitionrlv'ilue, the audionbeingalso adjusted:1 so" a'sgtjo be on 1theverge ofo's cillating-,because theselectivity andf-s'ensitivcfness Willuthen.begreatestY Tlielculve'sotFig;- jfor this case j:represent1th lf eantennavoltagejsrequired-ffor.a'given "es-pense i'n the tis :tojfbrthe least.l (whentheflocal cir'itfis'ne'arlyin tune -zwith the signa-lai. orftransitio icou-'f'.-...eVith zthe a'ifdiontosiillating the saine" ,apply 4:toireceivingfisustain'ed wave signals, ,esp eciallj7 ,fof short?Wave-length?? 'f Trans-i coupling;- lis'iafdvantaggeons*when. it isdesired'toeniployi looseljbouple .circuit-sz in` transniiitting.;sustained-waves .produced by an/audion For il'nclosei coupling' -isenvployed, the oscillationj having two: natural f frequencie"s.islikelytosudd'nlychange-from." oneto4 thefother. d-ueVto?any-disturbance, thus causing great,1inconvenience;-anti,v on theothenv hand, if loosencouplingis employed, a

. smaller proportion 'oi-the oiitputL of the au-A 44dion;-radiated-:fronrtheiantenna:V Thisfi's illustnated by-thecurvzefof F.ig;4 showing the great for :1=0.02. as for'the transitionvalue,j`re1'ft'ile neTgYmditQ-di-,Wth different Values 7, v .fofcoupling,assumingthe cur-rent in the local circuititog-remain-constnt.-It Will 4be vseen l j that no increase of radiated-.energyoccurs Awhen.the coupling is [made 'closer rv than the as* i transition value, buttha-ta rapid decrease occurs when the coupling is looser. f

In` radotelephone v vsend-ing, "al: microphone transmitter ,36isinserted between Wire'Q? and the ground, and having its primarycoil 37on .co1'e`38 inductively related to 4'seconc'lary 39 lo# 4cated betxieenWire -23zand battery' 24. v In r vorderl to vary vthe.frequencyfon-radio tele-'f' graph sending by-f. 'the' 'compensating wave methods;:Jr-condenserv 42 is connected by Wire 41,=to azkev 43,' whichy isconnected to ground y bywirefl. l .f j

l For long distancecommunication it is preferable to; weaken theoscillation'yat the receiving end and strengthen that. at the sendingend, which byl reason ofthe transition couplin'g at each en'ldhelpstomaintain synchro- `nousoperaltilon; Iand gives greater sensitivefinessatthe receiving end.` Varmtlon 'of the imY strengt-h of voscillation is.effected, asabove descrl ed, by varyingthe grid battery 24, or by varymmutual induction between coilslO pensation to beadj'usted by'trial, suchas a variable capacity, or one connected in or out of circuitsimultaneously with changesin the' battery; i

For long distance two-way telephonie con munication without changes in`adjustment,"

' the modification shown in Figure 2 ma. be

vas

used, employing areceving 'and asen ing audion at each station, oranyother high-fre'- .quency generator, or arc in place of the 'send ingaudlon. In such case the hi h=frequency sending source shouldlpreferabiybe so connected as not toafect the receiving audion .at thatstation. This isefected by balancing the antenna. capacity, inductanoeand resistvance on both. s idesof point B by the con-f denser 3, lowercoil?,a and non-inductive re' sistance r, respectively and causing 4themu- .tual induction between the 'antenna-and.local circuits to -be'ually divided between` coil 5 and the two coils 2. This insures thatthe.oscillations caused by sending from transmitter 36 willbe transmittedthrough the in' ductive couplin of coils 50, 51, 52, and wire and thenceto the `antenna is figure jalso shows the ceiving audion,which.makesnodifference in 4 f the results obtained withthis invention, and

isequally applicable to Figure 1L From the foregoing description, itwillbe understood that the method* of synchronous loperation bytransition-couplin ,and the circuits herein selected as examp es, are4of decided advantagedn radio communication, not

ronly in 'cutting down interference, but in in'- 'creaslng the rangewith a 'given power, or reqpirmg yless power for a given range. Port- "ale outfits embodying this inventionhave extremely small` dimensions andlight weight and have many "advantages for military and field vWork, aswhere quick. communication may be .desired `between moving Ao-utpostsand acentral station. l

y What is claimed, is: v 5 f1. A'radio telephone s. stem hav-ing at a`F'station 'radiating and collecting means, a "single means forproducing osc1llat1oi1s 1n said 'radiating means and; amplifyingcollccted oscillations, meansfor detecting' the collected oscillations.l'and means for varying the radiated oscillations by voice modulation,

said oscillation producing means being continuously yin action.

- 2. A radio 'telephonefsystem having vata station asingle rradiatingand collecting element, a single meansfor vproducing oscillations insaid radiating "means and amplifyamplifyi other stdli ing @Ollctledscillation's, means .for detectoutgoing of il l`a" t= i`on'sy to bereceive and am pflified bythe ther 'audion and receiving and omingoscillations from the nd sending andl receiving means at e s ationoperable at will wi the Asame yc cuit adjustments.

. 4,. A rad lephone system employing at` 1w ,stations an audion jenerating ,80 outgoing oscillations to bel received andern plified bytheother audion and receiving andl amplifying "i omi'ng oscillations fromthe other statiq jeach audioncomprising a heated eleni'ent1`and two coldelements s'o con- 95 nccted in .theirfcircuit's as to generateoscillations of.' `relatively lar'e ower v'vithoutsubstantiallrf:jimpairing t e t etectionV of in\ coming oscilation's,and sending and 'receiving means'atfeachstation operable at will 9"withthe lSan'u'circuit adjustments.

5. radicmmunicating system having at a stationasirigle radiatingandc'ollecting element, an iiudionfor producing-oscillations in saidradiating element and amplifying col- U6 A lectedoscillations, thegridof said -audi'on being conducjtifvely connected to the filamentthrough circuit lmeansffor adjusting its average potential, means fordetecting the collected'oscillations, and means lfor var' ing-the |00radiated `oscillations to transmit inte ligence.

6. A radiofyc'ommunicating system having at astationa'fsingle radiatingcollecting element, an audion for producing `oscillations in saidradiating'element and 'ampli ing colf los lected oscillationathe gridlof sai audion being conductively connected to the filament throu hcircuit'means of low audio frequencyr1 rfadjusting itsaveragepotentia,means fordetecting the collected oscillations, and means for varyingthera'diated oscillations -to transmit intelligence.

7.- A radio communicating system` having at a station a single.radiating and `collecting element, an audion for producing oscillations11B insaid radiating element' andampl'iyingjcob -lected oscillations',the y'grid lof said audion being conductivcly connected to the filament"element, lanfa'ud-ion for producing oscillations in said radiatingelementandfamplifying'collected oscillations, the grid of said a-udionbeing conductively. connected tothe '13o' filament through a battery formaintaining the average potential of the grid negative and apotentiometer for finely adjustin said potential, means forldetectingthe col ected oscillations, and meansfor varying the radiatedoscillations to transmit intelligence.-

9. The method of attaining synchronism between a free electricoscillation produced in one circuit by a source of continuous electricoscillations and a forced oscillation impressed on a second circuit,which comprises tuning said circuits to the forced oscillation andcoupling said circuits in such manner that the coefficient of couplingis substantially equal to the power factor of the second circuit.

10. Apparatus for producing' or am lifying electric oscillationscomprising a dbvice capable of producing electric oscillations, acircuit in which oscillations are generated by said device, and a secondcircuit in tune with the first circuit and coupled therewith in suchmanner that the coefficient of coupling is approximately equal to thepower factor of the second circuit.

11. Apparatus for producing or'amplifying electric oscillationscomprising a device capable of producing electric oscillations, a

`local circuit in which oscillations are generl ated by said device, andan antenna circuit jin tune with the local circuit and coupled ltherewith in such manner that the c'oetlicient of'coupling isapproximately equal to the power factor of the antenna circuit.

12. Apparatus for producing or amplifying electric oscillationscomprising an audion capable of producing electric oscillations, a localcircuit in which oscillations are generated by the audion, an antennacircuit coupledv with the local circuit' in such mannerthat thecoefficient of coupling is approximately equal to the power-factor oftheantenna circuit, and means for varying the natural fre quency of thesetwo circuits while keeping in tune with each other.

13. Apparatus for relaying electric im vpulses comprising aV localcircuit, means for impressing oscillations thereon, and a tuned antennacircuit coupled to said local circuit in such man-ner that thecoefiicient of coupling is approximately equal to the power factor i ofthe antenna circuit.

14. 4Apparatus for radiotelephone receiving comprising a'tunedreceivingcircuit containing an oscillating audion tuned'in syn- I chronism withthe incoming signal, said cir-j cuit being coupled to the antennacircuit in such manner that the coefficient of coupling 'substantiallyequals the power factor ofthe antenna circuit, and a telephone receiverin' the circuit of the audion. L c. 15. Apparatus for radiotelephonereceiv- Y ing comprising a tuned receiving circuit con-V taining anoscillating audion tuned in synchronism with the incoming signal,said'cvir-jA ner that the coefficient of coupling substan' tially equalsthe power factor. of the antenna circuit, a telephone receiver in thecircuit of one of'saidcold electrodes," and means for controlling thestrength of oscillation.

. 17. Apparatus for radiotelephone receiving comprising a tunedreceiving circuit containing an oscillating audion having a hot` and twocold electrodes, an antenna circuit' coupled to the receiving circuit insuch manner that the coefficient of coupling substan' tially equals thepower'factor of the antenna circuit, a telephone receiver in the circuitof one of said cold electrodes, and a variable coupling between thecircuits of said cold' electrodes for controllingthe strength ofoscillation.

18. Apparatus for radiotelephone receiv-j ing'and sending comprising atuned circuit containing an oscillating audion having ahot and two coldelectrodes, an antenna circuit coupled to said local circuit in suchmanner that thecoeiiicientof coupling substantially equals the powerfactor of the antenna circuit, a telephone receiver connected in circuitwith one of said cold electrodes, and a telephone transmitter connectedin circuitwith the other cold electrode.

19.' Apparatus for radio receiving and sending with the same adj ustmentcomprising an antenna circuit, a locally. oscillating circuit coupledthereto containing a single evacuated vessel having a hot andtwo coldelectrodes, .the circuit of one of said cold electrodes oscillating inysynchronism* with said antenna'circuit and containing a receiver, andthe circuit of the other cold electrode containing means for varying-theoscillations radiated by the antenna to transmit intelligence.

20.- Apparatus ing an oscillating audion having a hot and two coldelectrodes, an4 antenna circuit cou pled to 4said local circuit in suchmanner that the'co'eicient of coupling substantially equals of-said'coldelectrode, and means forv vary- 'Ling thesftrength of oscillation.

1 521.- Apparatus for radio receiving and sending comprising a tunedcircuit contain- ""ing -anr oscillatin audion having a hot and? `twocold `electro es, a -tuned antenna-'circuit l H5 y for radio receivingand 'v sending comprising a tuned circuit containthe power factor of theantenna circuit, re-

coupled tosaid local circuit in such manner that the coeicientofcoupling substantially equals the power factor of the antenna circuit,

, a receiver connected to one of said cold electrodes, a transmitterconnected to the other of said cold electrodes, and a variable couplingbetween` the circuits of said cold elecceiver connected to saidoscillating receiving 23. Apparatus for radio communicationcomprisin anantenna circuit, an evacuated vessel having a hot and two coldelectrodes, an oscillatin .tuned local circuit containing one of said/cod electrodes and coupled to said antenna circuit in such manner that theco.-4

eliicint of coupling is substantiall equal to radiated oscillations insending.

24. In radiotelepliony, means for` radiat` ing and -collecting energy inthe\form of electromagnetic Waves, a single means for producingoscillations in said radiating means in synchronismwith the collectedradiations and amplifying the same, a telephone for receiving theamplified synchronous re` ceived oscillations, and a telephonetransmitter for varying the radiated oscillations whereby to receive andtransmit speech in duplex witlioutchange in circuit adjustments.

25.,In a station for radio telephony the combination of' a source ofcontinuous oscilbining. said oscillation with an incoming voicemodulated signal oscillation, and means responsiveto the combinedoscillations for detection. f

Signed at Hoboken, in the county` of Hudson and State`of New Jersey,this twentyseventh day of October, A. D. 1917.

LOUIS ALAN HAZELTINE.

lation, means modulating said oscillation by v vvoice control fortransmission, means com-

